With climate change, new and hitherto known diseases have emerged in Europe: Dengue fever and West Nile fever. These are dangerous viral diseases with the risk of multiple complications. They can reach Poland soon.
Dengue is a bit like measles – infection with the virus also causes rashes, aching muscles and joints, and headaches. Complications may include life-threatening hemorrhagic fever with bleeding or shock. The problem is that the dengue virus comes in four different strains and the transmission of the disease only gives immunity to the strain to which the patient has caught the infection; resistance to other varieties is short-term. The disease exhausts the body a lot and it happens that the infected person does not survive the re-infection. The disease can also affect the liver or heart, causing failure or inflammation.
West Nile fever may be mild or severe. In the first one, it resembles the flu: there is fever, pain in muscles, joints and headache, sometimes enlargement of the lymph nodes. In more severe cases, these symptoms are rapid, accompanied by nausea, vomiting, difficulty swallowing, muscle weakness, and disturbances in gait, coordination and consciousness. Complications may be meningitis and constant states of chronic muscular ailments, headaches, memory and concentration disorders, chronic fatigue, and depression induced in this way.
One insect is responsible for spreading both diseases – the Egyptian mosquito (Aedes aegypti). It carries both the flaviviruses, dengue fever and West Nile fever, as well as the malaria plague.
Transportation of mosquitoes in tires
According to scientists from the Swedish Umea Universitat, global warming has created perfect conditions for this mosquito to expand in Europe. Mosquitoes come to the Old Continent by various routes, e.g. near Groningen in the Netherlands, a large colony of them was discovered in the transport of tires brought for processing (probably illegally from Egypt). Currently, Egyptian mosquitoes find good living conditions in most European countries – with the exception of Northern Europe and the southern shores of the Baltic and the North Sea – and are beginning to transmit infections. A series of dengue infections in Madeira, where several thousand tourists and residents fell ill, proves that this disease is no longer a theoretical possibility, but something completely real. We are also seeing cases in southern France and Croatia, and it is only a matter of time before such diseases will spread throughout the European Union as a result of the expansion of aedes aegypti, said Dr Preet.
The same happens with West Nile fever. According to the European Center for Disease Prevention and Control based in Stockholm, in the season 2012/2013 there were as many as 242 cases of West Nile fever infections in Europe. Cases occurred in Italy, Croatia, southern and central France, southern Germany, Greece, Albania, Portugal and Spain. The farthest lineage of the disease is northern Austria, with two cases, and southern Bohemia, with one case. Sick people were not tourists and did not go anywhere, which means that they could only get infected on the spot. Two Greek cases show that Aedes aegypti is colonizing viruses in Europe. First, a 74-year-old woman living in Palaio Faliro in the southern suburbs of Athens fell ill, then a 55-year-old man living in Southeast Athens. These people did not travel anywhere and at the time of falling ill, they had been staying in their place of residence for at least 2 months. According to the Greek governmental infectious disease agency KEELPNO, this shows that an Egyptian mosquito colony has formed in southern Athens. The city authorities ordered spraying against mosquitoes, but due to the crisis and lack of funds, they were local in nature.
The fate of the United States and Canada awaits Europe, according to Dr. Cory Morin and Andrew Comrie, of the University of Arizona. There, Dengue and West Nile fever have settled down with Egyptian mosquitoes for good since 1999. Now the viruses have reached the central provinces of Canada along with the mosquitoes. It is comforting for scientists that in the case of the US population as much as 70 percent. infected pass through the infection asymptomatically, which they attribute to the genetic difference of the populations living in the USA and Canada from the African populations. However, there are many infections – only in Texas in 2012, 1868 people were infected with West Nile fever, who saw a doctor. It is not known how many cases there were at all. Cory and Morin’s team believe that only the 30 percent that go to doctors. people who are more seriously ill. The fact that in the USA, despite the large number of cases, there are few cases requiring medical intervention, it may be a local feature. It may be different in Europe, say Cory and Morin.
In Poland, it has not been found yet
Prof. Włodzimierz Gut, PhD in virology from the National Institute of Hygiene. For most infections such as West Nile Fever, symptoms are non-specific or absent; infections are only severe or very severe from time to time. And here the problem arises – to what extent such a course of the disease is related to the genetic history of a given population. We remember the history of measles: in Europe, the disease of young children, in South America, it devastated entire Indian tribes. Since we are not able to predict which variant of the virus we will be dealing with or what its effects will be, it may turn out that the course of possible fever infections in our country will be milder than in Africa. But it may also turn out to be heavier than there – said MedOnet prof. Gut.
In his opinion, there is a risk that dengue fever and West Nile fever will reach Poland, but it is currently impossible to judge how soon it will happen.
Until a confirmed case of West Nile Fever occurs, it cannot be said that this disease actually occurred in Poland. West Nile fever has already been identified in Belarus, but it is not clear what the case may be – a warning against too hasty alarms could be an accident at London Heathrow Airport, near which there was a malaria accident caused by surviving mosquitoes flight from Africa. However, because the vectors had not formed a habitat, the disease was extinct. But it is true that we are dealing with a lottery – if the disease really got to us, only we will know how to find the virus and identify it. And it is not simple: serologically, tick-borne meningitis is also included in the group of flaviviruses, which include the West Nile fever and Dengue viruses. So mistakes can occur, and the only test that can give an unambiguous answer – neutralization – requires very specific test conditions – said Prof. Gut.
Tekst: Marek Mejssner
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